Table of Contents

Roof Construction Techniques: Pro’s and Con’s ...... 2 : Special Benefits for Architects and Engineers ...... 4 Special Benefits for Contractors and Builders ...... 5 Special Benefits for the Owner...... 5 How Does A Work? ...... 6 Typical Systems...... 8 Framing Variations ...... 11 Hip Set Framing Variations ...... 13 Additional Truss Framing Options Valley Sets ...... 15 Piggyback Trusses ...... 17 Typical Truss Configurations ...... 18 Typical Truss Shapes...... 20 Typical Bearing / Heel Conditions Exterior Bearing Conditions...... 21 Crushing at the Heel ...... 22 Trusses Sitting on Concrete ...... 22 Top Chord Bearing...... 23 Mid-Height Bearing ...... 23 Leg-Thru to the Bearing...... 23 Tail Bearing Tray...... 24 Interior Bearing Conditions ...... 24 Typical Heel Conditions...... 25 Optional End Cosmetics Level Return...... 25 Nailer ...... 25 Parapet...... 26 Mansard ...... 26 ...... 26 Stub ...... 26 Examples ...... 27 Erection of Trusses ...... 29 Temporary Bracing ...... 30 Checklist for Truss Bracing Design Estimates ...... 32 Systems ...... 33 Typical Bearing / Heel Conditions for Floor Trusses Top Chord, Bottom Chord, and Mid-Height Bearing...... 34 Interior Bearing Conditions ...... 35 Ribbon Boards, Strongbacks and Fire Cut Ends ...... 36 Steel Trusses ...... 37 Ask Charlie V...... 38 Charlie’s Advice on Situations to Watch Out for in the Field...... 41 Glossary of Terms...... 42 Appendix - References...... 48 1 Builders, Architects and Home Owners today have many choices about what to use in and floor systems

Traditional Stick Framing – Carpenters take 2x6, Truss Systems – in two primary forms: 2x8, 2x10 and 2x12 sticks of to the job • Metal Plate Connected Trusses – site. They hand cut and fit this lumber together Engineered trusses are designed and into a roof or floor system. delivered to the jobsite with a truss placement plan. Trusses are quickly erected and braced Timber Frame – Craftsmen assemble timbers, onsite. joinery and braces together to form a self- supporting skeleton . • Steel Trusses – Light gauge steel trusses are designed and delivered to the jobsite with a Products – I-, Glulam, truss placement plan. Trusses are lightweight, and LVL () wood products able to be quickly erected and braced onsite. are shipped to the jobsite, cut to fit, and made into beams for the floor system, or into ridge beams and sloping joists for the roof system.

Each method has advantages and disadvantages. In this book we will look at those pros and cons, and assist you in identifying which method is best for your situation. We hope to be able to offer you strengths for each system that can help you sell the value-added difference in the product you choose, as well as help you gain a better understanding of the roof systems themselves, with “real world” advice on framing techniques and issues. ______Pros ______Cons ______

Stick Framing Lowest cost for materials. Slow to install and requires if you have the time and the skilled labor. skilled labor required. May not be accepted by the If trusses cannot be delivered building department, as it is to the jobsite, conventional not an engineered product. framing may be your only Requires scarce large lumber alternative. sizes (2x8, 2x10) Smaller span capability. High jobsite waste.

Timber Frame Creates handsome exposed Slow to install and requires Timber Frame timber-frame . skilled labor. Difficult to run ductwork, wiring, pipes through. Slow to install and frame in. Hard to insulate

2 ______Pros ______Cons ______Engineered Wood Products I-Beams are suitable for steep Difficult to run ductwork, Wood Products sloping . wiring, pipes through. Trim-able ends on , great Limited use in complicated roof for angled or rounded walls. lines, coffered ceilings, etc. Engineered product with May require special connections. uniform quality. Glulam and Laminated Veneer Lumber make strong material.

Wood Trusses Lowest overall cost. You will want to plan things in advance. You’ll need a set of Fast to install. plans for the structure, and Requires ordinary tools and your walls should be close to doesn’t require skilled labor to where they’re supposed to be. install. Virtually any roof and is possible. Engineered product.

Steel Trusses Lightweight and stiff, so More expensive than metal Steel Trusses installing is easy and fast. connector plate wood trusses. May be preferred in light If not analyzed/designed by a commercial / industrial leading industry software settings for fire rating. program, the joint connections may be suspect. Straight ceilings for ceiling attachment. Virtually any roof and ceiling is possible. Engineered product. 3 Trusses: Special Benefits for Architects and Engineers

Trusses bring virtually unlimited architectural Trusses span longer than conventional framing, versatility, providing simple solutions to complex so you have more open space to work with in designs and unusual conditions without inhibiting the interior. building design freedom. Using trusses, you Truss manufacturers using Alpine software are have complete flexibility in interior room available for consultation when special framing arrangements, too. Using Alpine’s proprietary situations arise. VIEW software, truss designers can produce engineered shapes that satisfy virtually any Wood trusses connected with metal plates enjoy aesthetic and functional specification by the an outstanding record of more than 35 years of building design professional. proven performance and durability.

Trusses are an engineered and tested product. State of the art truss design software allows There are nationally recognized standards for truss manufacturers to design them to be: design and manufacturing of metal plate • Hurricane-resistant, and/or connected wood trusses. These standards have • Withstand heavy snow loads, and/or been adopted by major model building codes. • Support storage areas above the ceiling. This ensures a quality product. Alpine Professional Engineers are committed to providing the highest You can get a one- or two-hour fire rating with quality, cost efficient structural products for trusses using the FR-Quik System. your clients.

4 Special Benefits for Contractors and Builders

Trusses go up faster and easier, with less skilled conventional framing, sealed truss designs are labor requirements, no matter how complicated easily inspected. the roof or ceiling is. Trusses are lightweight and easy to install, Trusses put you under roof faster, which helps in requiring only normal construction tools. drawing construction loans. The wide nailing surface of 4x2 floor trusses safely The use of preassembled components generates speeds and flooring installation. less waste at the jobsite. This improves safety Expenses are accurately controlled because truss and reduces cleanup costs. On-site losses costs can be predetermined. from mis-cutting, theft and damage are virtually eliminated. Open web design allows easy installation of plumbing, electrical wiring and heating/cooling Trusses are built in a computer-aided ductwork. manufacturing environment to assure accuracy and quality. Trusses are available locally for fast delivery. More than 550 truss manufacturers throughout the Industry standards for manufacturing and handling United States and Canada are backed by the assure code-compliance. Building departments expertise of Alpine Engineered Products, Inc. recognize these standards and respect the software used to design trusses. While many building departments are wary about inspecting

Special Benefits for the Owner

The owner can enjoy peace of mind, knowing that Floor trusses can conceal mechanical services, the trusses have been professionally engineered leaving a clear plane for ceiling installations. This is and quality manufactured for the specific job. ideal for finished rooms in a lower level.

The resiliency of wood provides a floor system that Trusses provide clear spans so interior walls can is comfortable. be moved easily during remodeling or when making additions. It is very economical to remodel Wood is a natural insulator because it is composed homes with trusses, versus frame houses. of thousands of individual cells, making it a poor conductor of heat and cold.

Roof truss details such as tray, vaulted or studio ceilings improve the appearance and comfort of homes, offices, churches and commercial buildings.

5 How Does a Truss Work?

A truss is a frame that supports loads by efficiently Trusses can span up to approximately 90’, transferring its to end supports. While stick although very long truss spans are more framing might use larger 2x8, 2x10, etc. members challenging to deliver, erect, brace and install (which are expensive and hard to find without properly. While longer trusses may be “wobbly” as going into old growth forests), and might require they are lifted off of the ground and onto the either additional beams or interior load bearing bearing walls, once they are properly braced, the walls, trusses can span a longer distance without truss system is extremely strong. additional supports, while using less expensive and more plentiful 2x4 members, usually arranged in intersecting triangles.

Most truss manufacturers utilize sophisticated truss design software that is capable of designing the truss system as well as the truss itself.

The truss designer will work from a set of plans, first creating a truss placement plan, and then designing each truss in the system.

6 The job is manufactured and delivered to the jobsite, where the contractor / builder erects them and then quickly braces them.

Cutting the lumber Manufacturing the trusses

Delivering a truckload of trusses Erecting the trusses on the jobsite

7 Temporary bracing system Permanent bracing system Typical Framing Systems

Truss framing systems, and the names associated The illustrations below are designed to help you with them, vary all over the country and visualize typical framing systems, looking at: throughout the world. No matter how they are • A truss placement plan, framed or what they are called, though, truss • The overall 3D look of the roof planes in that systems easily provide tremendous flexibility in the roof system, and look of the roof system. • 3D view of the framing system of trusses.

______Gable ______(* See also – Gable framing variations) The most basic (and least expensive) of roofs, a find a gable frame on either end, each supported rises vertically on the shorter ends of by the continuous underneath it, and common the building, with sloping planes on either side, trusses in between, each of which spans from one which meet in the middle. In our example you’ll wall to the other.

This roof system could have a sloping ceiling or tray ceiling, if desired. 8 ______Hip set ______( * See also – Hip set framing variations )

______Dutch () Hip set ______Notice the vertical rise in the middle of the hip set end plane.

9 ______Tudor Hip ______A tudor hip provides some interesting sloping planes at either end, and is generally cheaper to build than a full hip set.

______Floor system ______( * See also – Floor Truss Systems )

10 Gable Framing Variations

______Dropped gable ______If the roof eave extends beyond the end wall the builder can run outlookers from the fascia and enough to require support for the roof sheathing, back to the first common truss. This provides then a dropped gable is specified. The top chord enough additional support for the sheathing. of the gable end is dropped down enough so that

______Clear Span Gable ______

While most gable ends have continuous support walls, but it also needs to have vertical gable studs under their bottom chords, a clear span gable to help the gable sheathing resist lateral wind must span from one wall to another. It has to have forces. diagonal webs to help distribute the load out to the

Alternative methods for framing a structural gable include the truss manufacturer providing a full gable truss (with just gable studs) and a full common truss, which would be fastened together with the gable end facing the wind, or providing studs along the outside face of a common truss. 11 ______Transition gable ______

A transition gable end truss occurs when a run of smaller span area of that same gable, it doesn’t smaller span trusses leads up to parallel longer have continuous support under its bottom chord. span trusses. The first longer span truss will face A transition gable, therefore, has diagonals to help lateral wind loads in the area where it is not transfer loads in the smaller span area, and gable shielded by the smaller span trusses. In the studs in the part that faces the wind.

12 Hip Set Framing Variations

Under the planes of a hip set roof, there are many builder preferences, manufacturing efficiencies, different methods used to frame the trusses. cost, and ceiling requirements. Some of the most Preferences for any given system hinges upon common hip systems are outlined below.

______Stepdown ______

A stepdown hip set provides a truss, with a hip jack running from the corners up the ridge until they meet the hip girder.

The builder must provide support for the hip ridge, usually in the form of blocking, or hip cats, in between each hip truss up to the peak.

______Midwest ______

The Midwest hip set also provides a girder truss, Hip cats must be field cut and installed with hip trusses that step up to the peak. between the hip trusses if a dropped-in gable is not provided (for more info see However in a Midwest hip set, you run a up Dropped-In Gable) from the corner of the front wall to the hip girder.

All the bottom chords of the end jacks run to the hip girder, allowing for better attachment of the drywall on the ceiling.

______California______

Notice that a long rafter is provided for the length of the hip ridge so no cats or field support of the ridge is necessary.

All the bottom chords of the end jacks run to the hip girder, allowing for better attachment of the drywall on the ceiling, and the top chords of the end jacks run all the way up to the hip ridge. Proper support of extended top chords is critical. 13 ______Northeast ______

In a northeast hip set, you will find a short jack starting at the corner and running up the hip ridge. This hip jack stops at a sub-girder. All end jack bottom chords run to the hip girder, allowing for better attachment of the drywall on the ceiling. Hip cats must be field cut and installed between the hip trusses. Works well with dual-pitched hip systems.

______Terminal ______

Terminal hip sets are used in spans up to about 30' to 32'. A ridge rafter runs from the corner up to the peak of the hip, and a sub-girder, located about half way to the peak, carries the side jack bottom chords while their top chords run up to the ridge rafter.

______Standard Terminal ______

The standard terminal hip set is used for very small spans, i.e. up to about 18’ to 20’. The two hip jacks running up the corners and the center end jack all connect at the peak, which can make the peak connection difficult on longer spans.

14 ______Drop-in Frame ______

An alternative method for providing support up the The frame fits in the plane of the front face of the ridges of a hip set is for the truss manufacturer to hip set, and provides additional rigidity to the roof

1 drop the flat top chord of the hip trusses by 1 /2 ”, system. Nailing sheathing into the 2x4 flat studs is and provide a special purlin frame (in red) for the also convenient. framing crew to drop in above the hip girder.

Additional Truss Framing Options

Valley Set – A valley set is a group of trusses which valleys, we would have an empty “hole” in the roof sit on top of other trusses in order to change the behind the girder. This would need either stick way the roof looks. In the example below, without framing, or a valley set.

15 Here is what the roof looks like after the valley set (in red) is added.

The top chords of the trusses which the valley set sits on must be braced, either by under the valleys, or by alternate bracing.

Images courtesy of Simpson Strong-® 16 ______Piggyback Trusses ______

When roof trusses are too tall to be manufactured Special diagonal bracing on the underside of the and/or delivered, truss manufacturers will “cap” top chords (in red) helps brace the the trusses and provide piggy back trusses. The themselves, and keeps them from shifting out of piggybacks below are shown above the roof so plane. that the purlin and bracing system can be seen.

Detail of the bracing system, with purlins (blue) and diagonal braces (red).

Hip truss shown with piggyback (field applied) 17 Typical Truss Configurations

18 19 Typical Truss Shapes

The outside profile of your truss can take on just about any shape you can imagine. Some of the more common truss shapes appear below.

20 Typical Bearing / Heel Conditions

Exterior bearing conditions - The illustrations below show typical support conditions.

• “Typical” Bottom Chord end condition

Typical conditions include a truss heel without an overhang, and/or with a raised heel, and/or with a sloping ceiling, for example:

Bearing support types for each can be any of the following:

Image from Alpine’s VIEW® software 21 Additional conditions and options include:

• Crushing at the heel - Sometimes the forces grain is running up and down, which has a higher transferred through the wood into the bearing shear value), or unless the bearing itself is made wall are enough to cause the wood to crush over wider so the forces are transferred through more time, unless either a bearing block is used, or, on surface contact area between the truss heel and a raised heel condition, the end vertical is run the bearing. through to the bearing wall (so the wood

• Trusses sitting on concrete walls - When the truss sits on a concrete wall, a seat plate may be required as a moisture barrier:

Images courtesy of Simpson Strong-Tie® 22 Other Bottom Chord Bearing conditions:

Truss in a hanger: Truss nailed to a girder/ledger (Right end):

• Top Chord bearing – Trusses can be designed to have support right under the top chord. You will want to shim the bearing solid under the top chord of the truss.

• Mid-Height bearing – Sometimes the bearing • Leg-Thru to the bearing – If the bearing is sits between the top and bottom chord of the below the truss bottom chord, the end vertical of truss, and a mid-height bearing block (the 2x6 the truss can extend down to sit on the bearing. vertical shown here) will be used. Special bracing may be required.

23 • Tail bearing tray – If the room calls for a tray or calls for a scab to be attached (an additional coffered ceiling very close to the edge of the piece of wood nailed to the face, or both faces, room, the truss can look like these tail bearing of the top chord at the heel, as shown by the tray trusses below. The example on the right hatched pattern).

Interior bearing conditions

Interior bearing

Two trusses sharing a wall

Built-in kneewall (see 3D image}

Special Connection Notes: designed for this purpose. These products • It is important to properly tie down the truss to should not only anchor the truss into the wall, your bearing walls, and not just in areas prone to but also tie the truss down to resist both uplift hurricanes. There are many products that are and lateral forces.

Images courtesy of Simpson Strong-Tie® 24 ______Typical Heel Conditions ______

• The top chord that extends beyond the bottom The outside cut of your overhang can look like any chord and bearing is called an overhang. of the images below.

Plumb Cut Square Cut Double Cut

Special Angle Cut Horizontal Cut

Optional End Cosmetics – In addition, the truss overhang can have optional cosmetic framing applied.

• Level Return: A level return is a horizontal member creating a under the overhang. The level return on the left side builds up the

1 fascia to 5 /2 ”, and uses a vertical to stiffen it. The level return on the right side creates a box soffit, and is plated to the raised heel of the truss.

• Nailer: If some trusses on the job have a 2x6 top chord, and some have a 2x4 top chord, you can keep a consistent fascia edge by applying a ripped piece of lumber to the under side of the overhang. This piece is called a nailer.

25 • Parapet: On trusses with raised heels, you can build in a parapet condition to your truss. This parapet can be used to either hide A/C units (on a flat truss, when the A/C unit is located on top of the ), or to hang signage. Additional bracing may be required for parapet conditions, especially in high wind areas.

• Mansard ends: For storefront signs or just for another look, special mansard jack trusses can be manufactured.

• and Stubs – Two common wall) and stubs (when there is a jog in the wall or conditions for trusses are cantilevers (when the some other reason why the truss would be held truss bottom chord extends beyond the outside back from its original span).

26 Bracing Examples

______Web Bracing ______

CLB: Continuous lateral bracing (CLB) is 1x4 or The CLB brace here is shown in blue, with diagonal 2x4 material nailed to the narrow side of a web. bracing to “brace the brace” shown in red.

CLB braces must be fastened across a minimum of The truss drawing will show a brace on the web, 3 trusses. If you don’t have a run of at least 3 and will also have a note specifying the brace, as trusses, you must use another type of brace. shown to the left here.

T-Brace: A T-Brace is 1x or 2x material fastened to the narrow face of an individual web so as to form a “T” shape.

(At right) Truss drawing depicting a T-Brace, and bracing note (below)

27 L-Brace - L-Braces are pieces of 1x or 2x lumber attached to individual webs to form an “L” shape. These braces are usually specified for gable ends, when one face of the truss will be sheathed.

L-Brace note from a truss drawing (below)

Scab Brace – A scab brace is applied to the wide face of the web member, using the same size lumber as the web itself.

Web Block® & Other methods for reducing field applied bracing – If you are open to reducing the amount of time your are in the roof system applying web bracing, and you don’t mind paying just a little bit extra for the truss package, the software used by truss fabricators allows them to use manufactured solutions like the Web Block (shown, at right), or to increase web grades and sizes to considerably reduce the need for field applied bracing. Talk with your local truss manufacturer about these alternatives! 28 Erection of Trusses

Trusses may be installed manually, by crane, or by forklift, depending on truss size, wall height and job conditions. Individual trusses should always be carried vertically to avoid lateral strain and damage to joints and members.

Trusses installed manually are slid into position over the sidewall and rotated into place using poles. The longer the span, the more workers needed to avoid excessive lateral strain on the trusses. Trusses should be supported at joints and the peak while being raised.

Large trusses should be installed by a crane or forklift employing chokers, slings, spreader bars and strongbacks to prevent lateral . Trusses may be lifted singly, in banded groups, or preassembled in groups.

Tag lines should always be used to control movement of trusses during lifting and placement.

Refer to Handling, Installing and Bracing Metal Plate Connected Wood Trusses (BCSI 1-02) by the Truss Plate Institute, or Wood Truss Erection poster by the Wood Truss Council of America for proper methods of installation.

Installation procedures are the responsibility of the installer. Job conditions and procedures vary considerably. These are only guidelines and may not be proper under all conditions.

29 Temporary Bracing

All trusses must be securely braced, both during There are two types of bracing. Temporary bracing erection and after permanent installation. is used during erection to hold the trusses until Individual trusses are designed only as structural permanent bracing, sheathing and ceilings are in components. Responsibility for proper bracing place. Permanent bracing makes the truss always lies with the building designer and component an integral part of the roof and contractor for they are familiar with local and job- building structure. Temporary and permanent site conditions and overall building design. All bracing includes diagonal bracing, cross bracing trusses should be installed straight, plumb and and lateral bracing. aligned at the specified spacing. Trusses should also be inspected for structural damage.

Permanent lateral bracing, as may be required by It is important to temporarily brace the first truss at truss design to reduce the length of the end of the building. One method calls for the individual truss members, is part of the truss top chord to be braced by ground braces that are design and is the only bracing specified on the secured by stakes driven in the ground, preferably design drawing. This bracing must be sufficiently outside and inside. The bottom chord is to be anchored or restrained by diagonal bracing to securely anchored to the end wall. Adjacent prevent its movement. Most truss designs assume trusses are now set connecting each to continuous top and bottom chord lateral support continuous lateral bracing on the top chord. These from sheathing and ceilings. Extra lateral and are typically spaced at 6’, 8’ or 10 feet on centers diagonal bracing is required if this is not the case. along the length of the truss. Refer to BCSI 1-02 for diagonal spacing. This top chord bracing will Bracing members should be 2x4 nailed with two 16d be removed as the sheathing is applied after the nails at each cross member unless specified otherwise other bracing is completed. on the design drawing. Lateral braces should be at least 10 feet long. Cross and diagonal braces should

30 run on an approximate 45 degree angle. Temporary bracing should be 2x4 dimension Inadequate bracing is the reason for most truss lumber or larger and should be 8 feet minimum in installation failures. Proper installation is a vital length. Continuous lateral bracing maintains step for a safe and quality roof structure. spacing, but without cross bracing, permits trusses These recommendations are offered only as a to move laterally. See BCSI 1-02. guide. Refer to Recommended Design To prevent dominoing, diagonal bracing should be Specifications for Temporary Bracing of Metal Plate installed in the plane of the webs as the trusses are Connected Wood Trusses (DSB-89) by the Truss installed. See BCSI 1-02. Plate Institute (TPI), or Handling, Installing and Bracing (BCSI 1-02) by TPI. For cold formed steel Full bundles of sheathing should not be placed on truss systems, refer to LGSEA’s two publications, the trusses. They should be limited to 8 sheets to Field Installation Guide for CFS Trusses, a pair of trusses. Likewise, other heavy and Design Guide for Construction Bracing of concentrated loads should be evenly distributed. CFS Trusses.

31 CHECKLIST FOR TRUSS BRACING

Bracing is extremely IMPORTANT!! Every roof Permanent Bracing which will remain installed for system needs adequate bracing. The purpose of the life of the roof system. most bracing is to ensure that the trusses and truss Temporary Bracing Guidelines: For metal plate members remain straight and do not bow out of connected wood truss systems, refer to BCSI 1-02 their plane. Inadequate, improper or incorrectly for proper installation bracing guidelines. For cold installed bracing can lead to collapses, failures and formed steel truss systems, refer to LGSEA’s two serious accidents. An engineered bracing system publications, Field Installation Guide for CFS will avoid these pitfalls and ensure the structural Trusses, and Design Guide for Construction integrity of the truss system. Bracing of CFS Trusses. Trusses need to be braced during installation, which is called Temporary Bracing, and they need

______Permanent Bracing System Checklist ______

1. Top Chord Planes  Do top chord planes have structural sheathing (plywood, OSB, metal deck)?  If not, do you have a purlin system, with both purlins (perpendicular to the trusses) and diagonal bracing? Purlin systems can be used for standing seam roofs, or with structural sheathing applied on top of the purlins. Either way, a diagonal brace system must be engineered. Refer to sealed engineered truss designs for specified purlin spacing.

2. Web Bracing – be sure to reference sealed engineered truss designs for proper web bracing callouts.  CLB Bracing crosses a minimum of 3 trusses, including diagonal bracing to “brace the bracing”?  Properly installed T-Braces, L-Braces (especially on gable ends), Scab Braces, and other web bracing systems such as the Web Block?

3. Bottom Chord Planes  Do bottom chord planes have structural sheathing directly attached? In many cases drywall is considered by the building designer to be lateral bracing, but in some cases it is not.  If not, then you will need a purlin system, which can be attached to the top of your bottom chords, and those purlins will need diagonal braces.  If you have any suspended ceilings, do you have a purlin system (including diagonal bracing) on the top or bottom of those bottom chords?

4. Additional Bracing Concerns  Piggyback Systems – If you have piggyback systems, do you have a purlin system installed to support the bottom chord of the piggyback, as well as purlins and diagonal braces to ensure that the flat top chords of the hip trusses stay in plane?  Valley Sets – Under the valley trusses, do you have structural sheathing, or other engineered bracing system for the top chords of the trusses underneath? Are the valley bottom chords adequately fastened down?  High Heel Heights at a Wall – for trusses with heel heights greater than a nominal 2x6, is special heel blocking required and installed?  Blocking For the Ridge in Hip Systems – Have you added blocks on the ridge between each hip truss (where a rafter or extended hip jack top chord doesn’t extend to the peak of the hip system) to support 32 the decking? Floor Systems

1 Another popular application for truss systems is in depths as well as a 3 /2” nailing surface. Some floor systems. Floor systems can be trussed, floors are built from 3x2’s, others from 2x4’s. conventionally framed, or built with engineered Floor trusses can be manufactured with many wood products such as I-Joists. Both trusses and different possible end conditions to accommodate engineered wood products are engineered, and different installation needs; around raised walls, have wider nailing surfaces for the floor decking. pocketed beams, headers around stairways, etc. Trusses are built with open chases for ductwork In addition, some manufacturers are taking and have natural open spaces for plumbing and advantage of adding an I- to the end of a truss electrical wiring. Some engineered wood to make it a trim-able end. Then the truss can be products have specified or marked notches that manufactured just a bit long, and easily trimmed can be removed to allow for the same. back as needed in the field. Two of the most Floor truss systems are sometimes called System common web patterns for floor trusses appear 42’s, because to build them manufacturers turn below: the 2x4’s on their side. This allows for shallow

Fan configuration web style Warren configuration web style

Is it OK to move a floor truss? Typical floor trusses where it was designed to be. When this happens, are engineered to be spaced evenly, and the truss please contact the truss manufacturer to be sure it design drawing will tell you how far apart the works. Sliding a floor truss even a few inches puts trusses are designed to be. Occasionally the need more load on the truss you’re moving it away from, will arise to shift one of the floor trusses from as shown in the drawing below.

Check with the truss manufacturer before shifting a truss !

IF YOU SHIFT IT: THEN THE OVERSTRESSED TRUSS CARRIES: B

24” 3” 6.2% more load than it was designed for 27” on center 6” 12.5% “ 30” trusses 9” 18.7% “ 33”

16” 3” 9.3% more load than it was designed for 19” on center 6” 18.7% “ 22” trusses 9” 28.1% “ 25” 33 Typical Bearing / Heel Conditions for Floor Trusses

______Exterior bearing conditions ______

• Bottom chord bearing – trusses can sit on a wall, or in a floor truss hanger.

• Top Chord bearing – When the bearing is raised under the top chord, the end can be built with or without an end vertical, and with or without an additional slider for extra strength.

• Mid-Height bearing – When the bearing is raised between the top chord height and the bottom chord elevation, the end will use either a solid 4x block of wood, or multiple 4x2 verticals at the heel. It can also be built with or without an end vertical, and with or without an additional slider for extra strength.

34 ______Interior bearing conditions ______

• This truss is supported by an interior load bearing wall.

• Cut chord condition – Over an interior load chord condition. This truss is designed to be cut bearing wall, a truss can also be built with a cut into two separate trusses in the field.

• Beam Pocket – This truss has a “pocket” built into it so the support can be recessed up into the truss.

• Threaded Beam – This truss has an opening designed and then threaded into the truss to help designed to bear on a beam, which will be support it.

35 ______Ribbon Boards, Strongbacks and Fire Cut Ends ______

• Ribbon Notches – Floor truss ends can have a trusses. By putting a 2x4 board at the end of the notch built into the top of the truss end, the first few trusses, the remaining trusses can bottom of the truss end, or both. The purpose easily be slid into place when they hit the of these notches is to help the line up the ribbon board.

• Strongbacks – A strongback helps to distribute • Fire Cut Ends – In some cases, floor systems the loads on a floor truss, thereby helping will be required to keep the top chord of reduce the “bounce” the floor system might the truss back away from the end otherwise have. Strongbacks are typically wall. In such circumstances, specified every 10’ to 11’ across a floor truss. As a firecut end can be provided, you can see in the image above, a strongback as shown here. has been attached to the verticals of the longer floor trusses. 36 Steel Trusses

While there are many steel truss solutions in the • Immune to insect damage, material deterioration marketplace, Alpine’s TrusSteel products are the and shrinkage, as well as from dry-wall pops. best, providing: • It’s an engineered product, so you can build with • Lightweight trusses: One worker alone can confidence! typically lift a 35’ truss by himself. TrusSteel trusses are easy to deliver, handle, and install. • The material is stiff, so installing drywall or other ceiling materials is easier. • Meets fire code non-combustible materials requirements.

JACK HANGER DETAIL UPLIFT ATTACHMENT TO STEEL UPLIFT ATTACHMENT TO STEEL 45° JACK HANGER SPRINKLER PIPE HANGER SPRINKLER PIPE HANGER

Bottom chord bearing jack to Bottom chord bearing truss to Bottom chord bearing truss to Bottom chord bearing jack truss Truss bottom chord hanger Truss top chord hanger detail girder truss (rated). steel girder connection (rated). header channel connection to girder truss connection detail (rated). (rated). (rated). (rated). 37 Ask Charlie V.

For nearly 46 years, Charlie Vaccaro has worked in virtually every phase of the truss industry. Originally an aeronautical engineer, he has designed truss connector plates and trusses, started truss plants, and as been an Alpine production consultant since 1970. Today, he serves as a speaker, author and National Sales and Plant Consultant for Alpine Engineered Products, Inc.

Strength-wise, what is the difference between floor plans, just by changing the trusses. The only conventional framing and trusses? Isn’t cost difference is the trusses, not the floor plan. I conventional framing as strong? am only showing you four; but, with imagination, I can do a few more elevations. CV: It should be, but, how do you know? Trusses are designed with 2 to 3 times the design If I have the resources, I can virtually work all load. They are calculated and tested to winter on homes by building the outside shell of perform at that level. The conventional the house in fair weather, and work on the inside framing depends on how good the during inclement weather and get a good day's carpenter in charge of the framing work done. If I was conventionally framing, my is. The only thing he knows about loading days would be more subject to the elements. is what's been done in the past from a Most people with construction loans don't get to skilled carpenter. Most don't have formal their first draw until the roof is dried in. Trusses will training today. get you there weeks ahead of conventional framing. Why use trusses? With trusses, if the square foot of the floor plan is CV: Trusses offer virtually unlimited architectural the same, no matter what I do to the floor plan, my versatility - complete flexibility of interior cost difference would be the cost of adding or partitioning and room arrangement - deleting a wall. Since trusses can span longer uniformity and accuracy from one truss to distances than conventional framing, I don’t often the next - faster and easier erection time - rely on interior load bearing walls, so you can lightweight (generally 20 to 40 percent less make changes to the interior without major than most other structural systems) - open problems. Plus, I can create heavy storage areas web design - durable. They have a proven above the ceiling if needed, without changing the performance record - inspectable and "total floor plan. in-place cost" savings.

Esthetically, I can take one basic floor plan Is it OK to cut a truss in the field? and leave it exactly the same. Yet, from the CV: Structural members of a truss should never outside, I can make it look like four different 38 be field cut without proper field repair engineering from the truss manufacturer. such as roof or floor sheathing, joists, or Non-structural members, such as overhangs purlins which contribute to the overall or filler bottom chords may be cut as long as rigidity of the roof or floor are in place. they do not interfere with the structural integrity of the truss. What is permanent bracing? CV: Permanent bracing is bracing that will be What is temporary bracing? installed in the roof system as a permanent CV: Temporary bracing is described as bracing part of the roof system. The most common in TPI's BCSI 1-02 as bracing which is is continuous lateral bracing which is a installed to hold the trusses true to line, member placed and connected at right dimensions, and plumb. In addition, angles to a chord or web to prevent buckling temporary bracing holds the trusses in a under loads less than design loads. Other stable condition until permanent truss examples are T-braces, L-braces, etc. bracing and other permanent components

ENERGY HEELS

SIMPLE STANDARD 12”

What are energy heels? time, plenty of room is available for air flow. The most important issue, of course, is providing the CV: An energy heel is a truss with a raised heel proper air flow (ventilation) so that condensation is to allow for proper ventilation with increased minimized. When the temperature difference insulation at the wall line. between the insulation space and the is large, A simple energy truss is one where the top the potential for condensation is great. Wet of the bottom chord just touches the bottom insulation loses its "R" value. It is imperative that of the top chord, with a wedge plated on. be well ventilated. This provides a raised heel of about 7-8 Typically, a baffle of or plastic is stapled inches, depending on the . This is the to the sheathing between the trusses to allow a cheapest way to go. clear path for air to flow. The baffle extends a little A standard energy truss will typically have a beyond the wall line past the point where the set heel height, such as 8 or 10 inches. insulation stops. On the inside, it extends along Typically, the end condition is made with a the pitch so that the outlet is above the insulation slider or a snubbed wedge. layer.

A 12" energy heel provides for the most One thing that helps the condensation problem is insulation and air flow. This is a good choice a moisture barrier on the ceiling. This prevents the for scissors trusses so that a good amount of warm, moist air from escaping into the attic. insulation can be applied; and, at the same 39 I’ve got to provide the truss manufacturer with CV: Your local truss manufacturer may already information so they can match some existing have a form to help you with this, but the trusses. What information will they need? one below is a good starter.

1) What is the Span of the truss? ______

2) Does the bottom chord of the truss run past the wall? Y N (circle one) a. If so, how far? ______

3) What is the Height of the truss? ______

4) What size is the top chord? 2x4 2x6 2x8 Not Sure (circle one)

5) What is the Heel Height? ______

6) Overhangs:

a. Put an overhang on One Side Both Sides None (circle one) b. Overhang length (measure horizontally) ______

c. Overhang type Square Cut Plumb Cut (circle one) (Note: Truss shown has a Square Cut overhang on the left, and a Plumb Cut on the right)

7) Vertical rise for every 24” horizontal run, measured using a level? ______(Please measure to within 1/8” accuracy)

Your Name: ______Phone: ______

Best Time to Call: ______Today’s Date:______

Any additional comments about this truss? ______

______

40 Charlie’s advice on situations to watch out for in • Deflecting , or incorrect fastening of the field: girder/beam plies – Multiple ply girders and beams MUST be fastened together BEFORE you • No purlins, or no lateral bracing under field put any loads on them!!! The truss drawing will applied piggybacks - You will need a braced provide instructions for the nail type you should system to keep the flat top chords of the hip use and the proper nail spacing for each trusses from bending out of plane (usually member (Top chords, bottom chords, and webs). purlins, as shown in blue), plus some kind of Also, if a bearing block is specified on any truss, bracing for those purlins (in red). Engineering be sure to install it! firms familiar with wood and/or steel truss systems, such as the Alpine Structural • Trusses installed backwards or upside down – Consultants, can assist in designing the right For any truss that could possibly be installed system. upside down, or backwards, take time to look at the truss drawings and find out how it was designed to be installed. If you have installed a truss backwards or upside down, either re-install it properly, or call the truss manufacturer ASAP to work together to resolve the problem.

• Lumber grade markings – Trusses are built with • Missing web bracing – If the truss drawing special engineered lumber grades, and the shows a web brace (CLB, T-Brace, L-Brace, Scab wood is stamped with that grade marking. If you brace) and hasn’t been applied, it needs to be don’t see those stamps on the wood, double applied! Refer to the truss drawing for brace check to see that it was built using the lumber size and connection information. grades and sizes specified on your engineered • No decking under a valley set – Remember truss designs. that it is important to brace the top chords of the • Missing plates, broken or cracked web trusses under a valley set. Apply sheathing members – Sometimes during handling a plate under the valley set, and attach the valleys well can fall off, or a web will crack, or a sub- to that sheathing. contractor can cut through a web to install • Leftover girders or other trusses on the electrical, etc. You should never cut a truss ground – If you have set all the trusses on the without consulting with the truss manufacturer. If roof but there are still trusses on the ground, you see any of these situations, contact your double check the truss placement plan, and call truss manufacturer for assistance in resolving the truss manufacturer. You may have missed these problems. Trusses are engineered to an extra girder ply, or they may have made a perform under designed loads, but they assume mistake. Either way, it’s important to be all the webs and chords are in good shape. confident that you have the roof system in Damage to a web or chord can require a repair place properly! (many times a simple repair for such conditions), in order for the roof to be structurally sound.

41 Glossary of Terms

AXIAL - A push () or pull () force acting along the length of a member [usually measured in pounds (lbs)].

AXIAL - The axial force acting along the length of a member, divided by the cross-sectional area of the member [usually measured in pounds per square inch (psi)].

BEARING – Anything which supports a truss; usually walls, hangers, beams or posts (shown in blue below).

BENDING - A measure of the bending effect on a member due to forces acting perpendicular to the length of the member. The at the given point along a member equals the sum of all perpendicular forces, either to the left or right of the point, times their corresponding distances from the point. Usually measured in inch-pounds.

BENDING STRESS - The force per square inch acting at a point along the length of a member, resulting from the bending moment applied at that point. Usually measured in pounds per square inch (psi).

BOTTOM CHORD - Horizontal or inclined members that establish the lower edge of a truss, usually carrying combined tension and bending stresses.

42 BRACING - See Lateral Bracing, Temporary Bracing, Permanent Bracing

BUILT-UP BEAM - A single unit composed of two or more wood members having the same thickness but not necessarily the same depth, which provides a greater load carrying capacity as well as greater resistance to .

BUTT CUT - Slight vertical cut at outside end of truss bottom chord made to ensure uniform nominal span and tight joints. Usually 1/4-inch.

CAMBER - An upward vertical displacement built into a truss, usually to offset deflection due to dead load.

CANTILEVER - The part of a truss that extends beyond its support. The truss below has a cantilever on the right.

CLEAR SPAN - Horizontal distance between interior edges of supports (see image above).

COMBINED STRESS - The combination of axial and bending stresses acting on a member simultaneously, such as occurs in the top chord (compression + bending) or bottom chord (tension + bending) of a truss.

CONCENTRATED LOAD - An additional load centered at a given point. An example is a crane or hoist hanging from the bottom chord at a panel point or mechanical equipment supported by the top chord.

DEAD LOAD - Permanent loads that are constantly on the truss, i.e.: the weight of the truss itself, purlins, sheathing, roofing, ceiling, etc. 43 DEFLECTION - Downward or horizontal displacement of a truss due to loads.

DIAPHRAGM - A large, thin that acts as a horizontal beam to resist lateral forces on a building.

DRAG - Typically a horizontal member, such as a truss or beam, which transfers shear from a diaphragm to a shear wall.

DROPPED GABLE – A gable truss that has its top chord lowered vertically to allow outlookers or a gable ladder to form an overhang.

DURATION OF LOAD FACTOR - An adjustment in the allowable stress in a wood member, based on the duration of the load causing the stress. The shorter the time duration of the load, the higher the percentage increase in allowable stress.

ENERGY HEELS – See page 39.

HEEL – The vertical height of the truss at the end of the span, measured from the top of the top chord to the bottom of the bottom chord.

HIP SET – A trussed system where three planes come in on a slope, so the outside planes look like this:

GABLE END – A truss with vertical studs, usually spaced 24” on center (or closer). The gable usually sits on an end wall and the studs help provide support for the sheathing and resistance to wind.

LATERAL BRACING - A member installed and connected at right angles to a chord or web member of a truss to resist lateral movement.

44 LEVEL RETURN - Lumber filler placed horizontally from the end of an overhang to the outside wall to form soffit framing.

LIVE LOAD - Any load which is not of permanent nature, such as snow, wind, seismic, movable concentrated loads, furniture, etc. Live loads are generally of short duration.

MID-HEIGHT BEARING – A Mid-Height bearing condition is when the elevation of the bearing that supports the truss is above the bottom chord, and below the top chord enough to require a short vertical, which will run from the top chord to the bearing.

OVERHANG - The extension of the top chord (usually) or bottom chord of a truss beyond the support.

PANEL - The chord segment defined by two successive joints.

PANEL LENGTH - The centerline distance between joints measured along the chord.

PANEL POINT - The centerline of the point of intersection in a joint where a web(s) meets a chord.

PEAK - Point on a truss where the sloped top chords meet.

PERMANENT BRACING – Bracing put on a roof or floor system that is intended to remain permanently on the roof to reinforce the structure.

PIGGYBACK – A cap truss provided which will sit on top of the trusses below (with purlins and blocking), usually when the trusses are too tall to build, or too tall to deliver.

PITCH – The slope of the roof, usually expressed as the vertical rise measured over a run of 12” (so if the roof 45 rises 6” vertically for every 12” inches horizontally). PLUMB CUT - Top chord cut that is plumb to the building floor line provided for vertical installation of a fascia.

PURLIN - A horizontal member in a roof perpendicular to the truss top chord used to support the decking.

REACTION - Forces acting on a truss through its supports that are equal but opposite to the sum of the dead and live loads.

RIBBON NOTCH – See page 36..

RIDGE – A ridge is the line formed when two planes meet.

SHEARWALL - A wall element that acts as a large vertical beam, cantilevered from the foundation to resist lateral forces on the building.

SLOPE (Pitch) - The inches of vertical rise in 12 inches of horizontal run for inclined members, generally expressed as 3/12, 4/12 etc.

SPAN – The length of the truss, measured from outside bearing to outside bearing, except in the case of cantilever conditions. If the truss is cantilevered beyond an outside bearing, the Span length would include the length of the bottom chord beyond the outside wall.

SPLICE (Top or Bottom Chord Splice) - The point at which two chord members are joined together to form a single member.

SQUARE CUT Overhang - A cut perpendicular to the slope of the member at its end.

46 STUB – When the truss is held back from its original span. SYSTEM 42 – A truss (usually a flat truss) where the 2x4 members have been rotated 90 degrees onto their sides, resulting in a truss that is 3 _” wide instead of 1 _” wide. These trusses are usually used floor systems, but can be provided as roof trusses because you can achieve shallow depth trusses when you utilize System 42s. These trusses can sometimes be manufactured using 3x2 lumber instead of 4x2 lumber.

TEMPORARY BRACING – Bracing added to the roof or floor system to brace it during erection and installation.

TOP CHORD - An inclined or horizontal member that establishes the upper edge of a truss, usually carrying combined compression and bending stresses.

TOP CHORD BEARING – Any time the bearing rests directly under the top chord of the truss. The image on the right is also often referred to a “tail bearing” truss.

TRUSS - A manufactured component that functions as a member. A truss employs one or more triangles in its construction.

VALLEY SET - Trusses built to change the look of the roof system, which sit in a perpendicular direction on top of other trusses.

VIBRATION - The term associated with the serviceability of a floor. If the occupant feels the floor respond to walking or other input, it may be referred to as vibration or response to load.

WEBS - Members that join the top and bottom chords to form the triangular patterns that give truss action, usually carrying tension or compression stresses (no bending).

47 Appendix B – References

American Forest & Association (AFPA) Southern Forest Products Association (SFPA) 202/463-2700 www.afandpa.org 504/443-4464 www.southernpine.com 1111 19th St. NW, # 700, Washington, DC 20036 P. O. Box 641700, Kenner, LA 70064 • National Design Specification for Wood Construction • Southern Maximum Spans for Joists and (NDS) • Southern Pine Use Guide • Wood Frame Construction Manual Southern Building Code Congress International, Inc. (SBCCI) American National Standards Institute (ANSI) 205/591-1853 www.sbcci.org 212/642-4900 web.ansi.org 900 Montclair Road, Birmingham, AL 35213-1206 11 West 47th Street, New York, NY 10036 • Standard Building Code • See TPI • Wind Design Standard, SSTD 10-93 APA - The Engineered Wood Association Truss Plate Institute (TPI) 206/565-6600 www.apa.wood.org 608/833-5900 www.tpinst.org 1119 A Street, Tacoma, WA 98401 583 D’Onofrio Drive, Suite 200, Madison, WI 53719 • Use of Rated Sheathing in Roofs & Floors • National Design Standard for Metal Plate Connected • Fire Rated Systems Wood Truss Construction, ANSI/TPI 1-2002 • Diaphragm Design • Standard for Testing Metal Plate Connected Wood Trusses, ANSI/TPI 2-1995 American Society of Civil Engineers (ASCE) • Recommended Design Specification for Temporary www.asce.org Bracing of MPC Wood Trusses, DSB-89 1801 Alexander Bell Dr., Reston, VA 20191-4400 • Handling, Installation and Bracing Metal Plate Connected • Minimum Design Loads for Buildings And Other Wood Trusses, BCSI 1-02 Structures, ASCE7 Western Wood Products Association (WWPA) American Society for Testing and Materials (ASTM) 503/224-3930 www.wwpa.org www.astm.org 533 SW Fifth Ave., Portland, OR 97204 1916 Rice Street, Philadelphia, PA 19103 • Western Lumber Product Use Manual • Test Methods for Fire Tests for Building Construction and Materials, E-119 Wood Truss Council of America 608/274-4849 www.woodtruss.com Building Officials and Code Administrators International, Inc. One WTCA Center (BOCA) 6300 Enterprise Ln., Madison, WI 53719 708/799-2300 www.bocaresearch.com • Metal Plate Connected Wood Truss Handbook 4051 W. Flossmoor Road, Country Club Hills, IL 60478 • Job-Site Bracing Poster - TTB Series The BOCA National Building Code Council of American • ANSI/TPI/WTCA 4-2002 Building Officials (CABO) ______703/931-4533 www.cabo.org Canadian References 5203 Leesburg Pike, # 798, Falls Church, VA 22041 Alpine Systems Corporation Corporation • One and Two Family Dwelling Code 905/879-0700 www.alpeng.com 70 Moyal Court, Concord, ON L4K 4R8 Forest Products Laboratory 1701 Creditstone Road, Concord, ON L4K 5V6 • Truss Design Procedures and Specifications for Light www.fpl.fs.fed.us Metal Plate Connected Wood Trusses (Limit States U.S. Department of Agriculture Design), published by TPIC One Gifford Pinchot Drive, Madison, WI 53705 • Wood Handbook: Wood as an Engineered Material Canadian Wood Truss Association - L'Association Canadienne des Fabricants de Fermes de Bois Gypsum Association 613/747-5544 www.cwc.ca 202/289-5440 www.gypsum.org 1400 Blair Place, Suite 210, Ottawa, ON K1J 9B8 810 First St. NE, # 510, Washington, DC 20002 • Wood Design Manual • Fire Resistance Design Manual, GA-600 Canadian Standards Association International Code Council (ICC) 416/747-4044 www.csa.ca 703-931-4533 www.intlcode.org 178 Rexdale Boulevard • Rexdale, ON M9W 1R3 5203 Leesburg Pike, #600, Falls Church, VA 22041 • CSA 086.194 "Engineering Design in Wood • International Building Code (Limit States Design)" • International Residential Code • CSA S347-M1980 "Method of Test for Evaluation of Truss International Conference of Building Officials (ICBO) Plates Used in Lumber Joints" 213/699-0541 www.icbo.com National Research Council of Canada 5360 S. Workman Mill Rd, Whittier, CA 90601 613/993-2463 www.nrc.ca/irc • Uniform Building Code Institute for Research in Construction • Uniform Fire Code 1500 Montreal Road • Ottawa, ON K1A 9Z9 NAHB Research Center • National Building Code of Canada (NBCC) 301-249-4000 www.nahbrc.org • National Farm Building Code of Canada (NFBCC) 400 Prince Georges Blvd., Upper Marlboro, MD 20774 ____ light Gauge Steel References ___ National Frame Builders Association (NFBA) Light Gauge Steel Engineers Association 913/843-2111 www.postframe.org 866/465-4732 www.lgsea.com 4980 W. 15th St., # 1000, Lawrence, KS 66049 1201 15th Street, N.W., Suite 320, Washington, DC 20005 • Frame Building Design • Field Installation Guide for CFS Roof Trusses • Post Frame Comes of Age • Design Guide: Permanent Bracing of CFS Steel Trusses 48 • Recommended Practices-Post Frame Construction

1100 Park Central Blvd. South Pompano Beach, FL 33064 800-521-9790 www.itwbcg.com

Nov. 1, 2010